For their high energy density per unit weight, alkaline batteries have widely been used as power sources of portable electronic devices which have rapidly been spread in recent years. Today, there are various alkaline batteries different in grades and price ranges adapted to different devices and applications, including regular alkaline batteries having a good discharge characteristic under a light load suitable for devices such as handheld game machines, high-performance alkaline batteries having a good discharge characteristic under a heavy load suitable for devices such as digital still cameras, and high-quality and high-performance alkaline batteries having a good discharge characteristic in a wide range from a high current to a low current.
A typical material as a positive electrode active material of the alkaline battery is electrolytic manganese dioxide (EMD). In order to provide batteries with a good discharge characteristic, various improvements and refinements have been done, e.g., by increasing a reaction area of manganese dioxide or raising a potential of manganese dioxide (see Patent Literature 1).    Patent Literature 1 Published Japanese Patent Application No. 2004-47445    Patent Literature 2 Published Japanese Patent Application No. 7-183032